Highly selective and efficient electrocatalytic synthesis of glycolic acid in coupling with hydrogen evolution

Armed with both hydroxyl and carboxyl groups, glycolic acid is an especially high-value-added chemical applied in diverse areas. However, its large-scale production suffers heavily from harsh synthetic conditions and poor selectivity. Here, an electrocatalytic approach has been developed for glycolic-acid production by electro-oxidation of ethylene glycol in alkaline solution on a PdAg electrocatalyst in situ grown on nickel foam (PdAg/NF). Resultantly, as low as 0.57 V versus reversible hydrogen electrode at 10 mA cm⁻² is needed for ethylene glycol electro-oxidation, which is markedly (980 mV) lower than that of oxygen evolution in the same electrolyte without ethylene glycol. Moreover, glycolic acid can be electro-catalytically produced most efficiently at an extremely high current density of 300 mA cm⁻² without the occurrence of oxygen evolution. When coupled with a Pt cathodic catalyst, a cell potential of 1.02 V is necessary for cathodic hydrogen production at faradic efficiency of 100%.